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Ankylosaurus
Ankylosaurus was a late Cretaceous ankylosaur. It was the size of an elephant. It lived alongside carnivores such as Tyrannosaurus rex but like all ankylosaurs was not in any danger from them due to it's armored back - which no carnivore would be able to bite through - and tail club, which could mortally injure a T. rex. Description In comparison with modern land animals the adult Ankylosaurus was very large. Some scientists have estimated a length of 9 meters (30 ft). Vickaryous, M.K., Maryanska, T., & Weishampel, D.B. 2004. Ankylosauria. In: Weishampel, D.B., Dodson, P., & Osmólska, H. (Eds.). The Dinosauria (2nd edition). Berkeley: University of California Press. Pp. 363-392.. Another reconstruction suggests a significantly smaller size, at 6.25 m (20.5 ft) long, up to 1.5 m (5 ft) wide and about 1.7 m (5.5 ft) high at the hip. Carpenter, K. 2004. Redescription of Ankylosaurus magniventris Brown 1908 (Ankylosauridae) from the Upper Cretaceous of the Western Interior of North America. Canadian Journal of Earth Sciences 41: 961–986. Ankylosaurus may have weighed over 6,000 kilograms (13,000 lb),Coombs, Walter P. (December 1978). "Theoretical Aspects of Cursorial Adaptations in Dinosaurs". The Quarterly Review of Biology 53 (4): 393–418. doi:10.1086/410790. making it one of the heaviest armored dinosaurs yet discovered. The body shape was low-slung and quite wide. It was quadrupedal, with the hind limbs longer than the forelimbs. Although its feet are still unknown, comparisons with other ankylosaurids suggest Ankylosaurus probably had five toes on each foot. The skull was low and triangular in shape, wider than it was long. The largest known skull measures 64.5 centimeters (25 in) long and 74.5 cm (29 in) wide.Carpenter, K. 2004. Redescription of Ankylosaurus magniventris Brown 1908 (Ankylosauridae) from the Upper Cretaceous of the Western Interior of North America. Canadian Journal of Earth Sciences 41: 961–986. Their teeth were weaker than ceratopsid and hadrosaurid dinosaurs of the time, so they probably chewed very little. Armor The armor of Ankylosaurus was made of huge knobs and plates of bone, known as osteoderms or scutes, embedded in the skin. Osteoderms are also found in the skin of crocodiles, armadillos and some lizards. The bone may have been covered by a tough, horny layer of keratin. These osteoderms ranged in size, from wide, flat plates to small, round nodules. The plates were lined up in regular horizontal rows down the animal's neck, back, and hips, with the many smaller nodules protecting the areas between the large plates. Smaller plates may have been on the limbs and tail. Compared to the slightly more ancient ankylosaurid Euoplocephalus, the plates of Ankylosaurus were smooth in texture, without the high keels found on the armor of the coexisting nodosaurid Edmontonia. A row of flat, triangular spikes may have stuck out sideways along each side of the tail. Tough, rounded scales protected the top of the skull, while four horns were behind the eyes and the ends of the mouth. Carpenter K. 2004. Redescription of Ankylosaurus magniventris Brown 1908 (Ankylosauridae) from the Upper Cretaceous of the Western Interior of North America. Canadian Journal of Earth Sciences, 41: 961–986. Tail club The tail club of Ankylosaurus was also made of large osteoderms, which were fused to the last few tail vertebrae. It was heavy and kept up by the last seven tail vertebrae, which joined to form a stiff rod at the base of the club. Thick tendons have been preserved, which attached to these vertebrae. These tendons were bony and were not very elastic, giving great force to the end of the tail when it was swung. It seems to have been an active defensive weapon, that could give enough of a harmful impact to break the bones of an attacker. Carpenter, K. 2004. Redescription of Ankylosaurus magniventris Brown 1908 (Ankylosauridae) from the Upper Cretaceous of the Western Interior of North America. Canadian Journal of Earth Sciences 41: 961–986. A 2009 study showed that large tail knobs could break bones on impact, but average and small knobs could not, and that tail swinging behavior is feasible in ankylosaurids, but it's still unknown if the tail was used for interspecific defense, intraspecific combat, or both. Arbour, V. M. (2009) "Estimating Impact Forces of Tail Club Strikes by Ankylosaurid Dinosaurs" PLoS ONE 4(8): e6738. doi:10.1371/journal.pone.0006738 It has been proposed that the tail club served as a false 'head' to lure potential aggressors within striking range, though this idea is still controversial. Thulborn, T. 1993. Mimicry in ankylosaurid dinosaurs. Record of the South Australian Museum 27: 151–158. Classification Ankylosaurus was named as the type genus of the family Ankylosauridae. Brown, B. 1908. The Ankylosauridae, a new family of armored dinosaurs from the Upper Cretaceous. Bulletin of the American Museum of Natural History 24: 187–201. Ankylosaurids are members of the larger taxon Ankylosauria, which also contains the nodosaurids. Ankylosaur phylogeny is a heated topic, with several mutually exclusive studies given in recent years, so the exact position of Ankylosaurus within Ankylosauridae is unknown. Ankylosaurus and Euoplocephalus are often thought to be sister taxa. However, other studies have found these genera in different positions.Carpenter, K. 2001. Phylogenetic analysis of the Ankylosauria. In: Carpenter, K. (Ed.). The Armored Dinosaurs. Bloomington: Indiana University Press. Pp. 454–483.Hill, R.V., Witmer, L.M., & Norell, M.A. 2003. A new specimen of Pinacosaurus grangeri (Dinosauria: Ornithischia) from the Late Cretaceous of Mongolia: ontogeny and phylogeny of ankylosaurs. American Museum Novitates 3395: 1-29. Further discoveries or research may clear up the situation. History Ankylosaurus was named by American paleontologist Barnum Brown, in 1908. The name comes from the Greek words αγκυλος/''ankulos'' ('curved') and σαυρος/''sauros'' ('lizard'). Brown intended this name in the same sense as the medical term ankylosis, to refer to the stiffness from the fusion of many bones in the skull and body, so the name is often translated as 'stiffened lizard.' The type species is A. magniventris, from the Latin magnus ('great') and venter ('belly'), referring to the great width of the animal's body. Paleobiology Ankylosaurus magniventris lived between 66.5 to 65.5 million years ago, in the final Maastrichtian stage of the Late Cretaceous Period, and was one of the last dinosaur species that appeared before the Cretaceous-Tertiary extinction event. The type specimen is from the Hell Creek Formation of Montana, while other specimens have been found in the Lance Formation of Wyoming and the Scollard Formation in Alberta, Canada, all of which date to the end of the Cretaceous. The Lance, Hell Creek and Scollard Formations represent different sections of the western shore of the shallow that divided western and eastern North America during the Cretaceous. They represent a broad coastal plain, extending westward from the seaway to the newly formed Rocky Mountains. These formations are composed largely of sandstone and mudstone, which have been attributed to floodplain environments.Lofgren, D.F. 1997. Hell Creek Formation. In: Currie, P.J. & Padian, K. (Eds.). The Encyclopedia of Dinosaurs. San Diego: Academic Press. Pp. 302-303.Breithaupt, B.H. 1997. Lance Formation. In: Currie, P.J. & Padian, K. (Eds.). The Encyclopedia of Dinosaurs. San Diego: Academic Press. Pp. 394-395.Eberth, D.A. 1997. Edmonton Group. In: Currie, P.J. & Padian, K. (Eds.). The Encyclopedia of Dinosaurs. San Diego: Academic Press. Pp. 199-204. The Hell Creek is the best studied of these ancient environments. At the time, this region was subtropical, with a warm and humid climate. Many plant species were supported, primarily angiosperms, with less common conifers, ferns and cycads. An abundance of fossil leaves found at dozens of different sites indicates that the area was largely forested by small trees.Johnson, K.R. 1997. Hell Creek Flora. In: Currie, P.J. & Padian, K. (Eds.). The Encyclopedia of Dinosaurs. San Diego: Academic Press. Pp. 300-302. Ankylosaurus shared its environment with dinosaurs including the ceratopsids Triceratops and Torosaurus, hypsilophodont Thescelosaurus, hadrosaurid Edmontosaurus, nodosaurid Edmontonia, pachycephalosaurian Pachycephalosaurus, and the theropods Ornithomimus, Troodon, and Tyrannosaurus. Weishampel, David B.; Barrett, Paul M.; Coria, Rodolfo A.; Le Loeuff, Jean; Xu Xing; Zhao Xijin; Sahni, Ashok; Gomani, Elizabeth, M.P.; and Noto, Christopher R. (2004). "Dinosaur Distribution". The Dinosauria (2nd). 517–606. Fossils of Ankylosaurus are quite rare in these grounds, compared to Edmontosaurus and the super-abundant Triceratops, which make up most of the large herbivore fauna. Another ankylosaur, Edmontonia, is also found in the same formations. However, Ankylosaurus and Edmontonia seem to have been separated both geographically and ecologically. Ankylosaurus had a wide muzzle, perhaps used for non-selective grazing and thus may have been limited to the upland regions, away from the coast, while Edmontonia had a narrower muzzle, indicating a more selective diet, and seems to have lived at lower elevations, closer to the coast. Ankylosaurus in The Land Before Time They are known as Clubtails to the Land Before Time dinosaurs. They first appeared in ''The Great Valley Adventure'', in the opening narration; one can also be seen lounging under a tree sweet tree during the credits. The most notable Ankylosaurus is Mr. Clubtail, aka Kosh. Land Before Time Ankylosaurus have some armor on their noses, two horn-like spikes on the top of their heads, two small spikes at the ends of their mouths, square-shaped armor-plates on their backs, spikes along their sides, pebble-like bumps in the corner of each armor-square, short legs and tails, and two-lobed tail-clubs. Gallery File:Clubtails.jpg‎|Two young clubtails, with others in background. File:Kosh_2.jpg‎|Kosh, also known as Mr. Clubtail. References External links *[http://www.newsgrape.com/a/ankylosaurus-the-bullet-proof-dinosaur/ Ankylosaurus- The Bullet-Proof Dinosaur'] *[http://web.me.com/dinoruss/de_4/5a7804b.htm Ankylosaurus in the Dinosaur Encyclopaedia] Category:Fourfooters Category:Dinosaurs Category:Fourfooters Category:Dinosaurs